This invention relates to a self-closing, linear, slideless fastener having resilient parts which at their respective locations serve for effecting the self-propagation of the boundary between zones of different states of connection (that is, separated state and joined state of the fastener).
In the above-identified related application slideless fastener arrangements are described wherein the connection is effected by a mechanical engagement, basically similar to the conventional slide fasteners or profile strip fasteners. In or between the movably arranged parts structured to perform the engagement function, there are provided resilient parts which in one of the two states of connection are in a tensioned condition and which, at the boundary between the two zones of different states of connection assume, during propagation of the boundary, a relaxed condition due to their particular position there and thereby cause a further propagation of the boundary.
An in itself separate class of fasteners was formed by arrangements wherein the two halves of the fasteners have a profile of constant cross section along the length of the fastener and the two halves are made of a continuous elastic material affixed to the two articles to be temporarily attached to one another. The elastic halves interengage in a manner similar to the profile strip fasteners but, viewed in cross section, they can assume different stable configurations with different elastic tension energy. These stable configurations are associated with the different states of connection so that the difference of the tensional energies furnishes the propelling force to cause propagation of the boundary.
The above arrangements of constant cross section may further be so structured and positioned as to improve various properties, particularly, to provide improved bending properties (flexibility). In general, arrangements having a profile of constant cross section, and their before mentioned generalizations, may be characterized in this manner: Along the fastener, at the individual articles, there extend coherent but sufficiently mobile (for example, flexible) parts or chains of parts of each fastener half. These parts or chains of parts will be hereafter generally referred to as elements. These are, among one another and transversely to the fastener, coupled by resilient parts in each fastener half. As the elements move with respect to one another, a transition is possible particularly from one state of higher spring bias into another state of a lower spring bias or no spring bias at all. The states may be stable even in the presence of spring bias by so structuring the elements that, for example, they may hook into one another or they may lie on interpositioned additional parts or they may retain each other in arrangements for the automatic dissolution of the connection or, at the respective locations the several tensioned parts mutually maintain their tension.
The states of the different tensions, as it was generally mentioned above, are associated with different states of connection of the fastener. They may also exist side by side along the fastener zones based on the mobility of the elements. Conversely, the retension (coherence) in the elements effects, viewed spatially, a not too discontinuous transition at the boundary between the zones of the different states of connection so that the tension at a location which is no longer in a stable state of high tension is still capable to pull out adjacent parts from the stable state of higher tension (for example, to unwind from a support). By virtue of contact between the elements of the different, temporarily connected portions of the fastener halves the relaxation (release of tension) cannot occur without an accompanying shift of the boundary between the different states of connection. In general, by shifting the boundary with an outer force, for example, by pulling the separated ends apart, this process can even be reversed. The above-noted contact functions may be performed to a greater or lesser extent by the adjoining zones of the resilient parts which are to be regarded as zones of the correspondingly-structured elements.
Fasteners having two elements connected to one another, by means of, for example, arcuate, deformable resilient parts are of particular significance. In self-closing fasteners, the elements mutually support one another in the tensioned state. These fasteners have been described in the above-identified related application as being longitudinally slit-open tubes, particularly of the type whose walls are made of an elastic material which may resiliently be bent away or towards one another and which may have additional structural features for performing other functions. The two elements are to be considered as being arranged at the edges or in the vicinity of the edges, whereas the bent wall constitutes the resilient connection. Thus, in the description below, longitudinally split tubes and their two edges are to be understood as having the above-discussed properties.
Fasteners of the above type for the self-closing of two articles have also been of symmetrical structure wherein the interengaging fastener halves were identically formed or at least were designed according to identically determined characteristics. These have the advantage that both halves have an active effect so that the cross section in general may be maintained at an overall smaller value. The two halves of the symmetric arrangements described earlier, however, are, in the connected state, hooked to one another to a greater extent at the edge so that the connection, based on a leverage effect, is more sensitive to outer effects. Further, the hollow spaces necessary for the motion of the springs in the fastener halves are present twice in the connected state and, viewed in cross section, particular structuring at the edges is necessary for the mutual holding effect and the mutual guidance at the boundary.